Doubt about terrain in scripting

Hello!
I'm fairly new at unity (only started a couple of days ago) and i was currently trying to mess around with terrain.
I was thinking of creating a script that would change with textures on my terrain object to create certain biome areas like desert, grass, snow.. Basically starting up the game and paiting my terrain on random areas with certain textures.
How can I target terrain areas and change the texture only in that area so that i can do what i described? is it possible?

Given that you use Unity's built-in terrain, you basically need to access the Terrain component and its associated TerrainData.
If you're also new to C# or programming in general, it may take a while to get something done. I'd then suggest to start with something that is easier.
Otherwise, if you have some programming experience, you should be able to prototype your system pretty quickly.